feat: Add creation_date column to characters table (#1825)

data/sql/updates/pending_db_characters/rev_1557608218190967100.sql

@@ -0,0 +1,4 @@
+INSERT INTO `version_db_characters` (`sql_rev`) VALUES ('1557608218190967100');
+
+ALTER TABLE `characters`
+	ADD COLUMN `creation_date` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP AFTER `grantableLevels`;